1. Field of the Invention
The present invention relates to a plate member carrier and, more particularly, to such a plate member carrier, which controls the lifting of the suction device by means of a simple harmonic motion.
2. Description of the Related Art
FIG. 1 illustrates an air cylinder type plate member carrier constructed according to the prior art. This structure of air cylinder type plate member carrier comprises a suction device 20 adapted to suck and transfer the workpiece, and an air cylinder 21 adapted to move the suction device 20 vertically up and down. This structure of plate member carrier is still not satisfactory in function. At the initial or end stage of the action of the air cylinder 21, the suction device 20 and the machine base produce noises and vibrations, and the workpiece, for example, printed circuit board 22 tends to be forced out of the suction device 20, causing damage to the printed circuit board 22 or the machine base. Furthermore, the air cylinder 21 starts to wear quickly with use.
The present invention has been accomplished to provide a plate member carrier, which eliminates the aforesaid drawbacks. It is one object of the present invention to provide a plate member carrier, which moves the workpiece stably without vibration. It is another object of the present invention to provide a plate member carrier, which produces little noise during its operation. To achieve these and other objects of the present invention, the plate member carrier comprises a suction device adapted to suck and transfer the workpiece, a first four-bar linkage adapted to keep the suction device in horizontal, a second four-bar linkage adapted to prohibit the suction device from transverse displacement, and a cam adapted to control vertical movement of the suction device subject to a simple harmonic motion curve.